KR19980071252A - Piston pump - Google Patents

Abstract

The present invention relates to reducing the concern of scaffolding of mutually reciprocating bearing surfaces that occur when transporting poorly lubricating media, for example fuels, especially gasoline.

The load reduction chamber 22 formed by the notch provided in the area | region of the slide surface 16 and the sliding bearing surface 17 is connected to the working chamber 25. As shown in FIG.

Description

Piston pump

The present invention relates to a piston pump, in particular a high pressure pump for a fuel injection device of an internal combustion engine, in which one or more pistons are installed, the pistons being movably supported in the casing, which divides the work chamber in the casing, and the casing A drive shaft is supported in the drive shaft, and a crank element is installed on the drive shaft, and the stroke ring is supported so as to allow rotational movement relative to the crank element, and the stroke ring cannot rotate in the casing, and the stroke ring corresponds to the piston. It relates to a piston pump having a sliding bearing surface arranged, the piston is supported on the sliding surface on the sliding bearing surface, the piston is loaded by the drive shaft.

In the case of the piston pump of the above-described type (the specification of JP 3522479), a plurality of pistons arranged in the molding are driven by one eccentric body. This eccentric is mounted on the drive shaft. This eccentric body is supported by a bushing ring which is not rotatable in the pump casing. The bush has bearing surfaces for each piston on its outer circumference. The bearing pad is supported by this bearing surface. Such a slide pad is supported by a steel plate attached to its corresponding end.

In the case of such known pumps, the supply of the medium to be pumped to and from the work chamber is done through the same conduit under the use of a control valve. In this case, the piston is against the stroke ring by the supplied medium to be fed.

In the case of such a piston pump, a rammer may be inserted into the cutout of the piston opened toward the stroke ring instead of the steel plate. The bar is mounted on the slide pad at the flange and is pushed to the stroke ring by a compression spring disposed inside the bar. Thus, even if the supply of the medium to be conveyed is interrupted, the push rod keeps in contact with the stroke ring and prevents the unwanted rotation of the stroke ring against the casing.

In order to generate the buffer effect, the bar is provided with a supply connection part and an axial hole. The oil can be supplied to the inside of the bar and the piston through this supply connection portion and the axial hole.

B. W. Goetz's Theory and Real Hydraulics (Hydraulik in Theorie und praxis. Von Bosch, 1983, published by Robert Bosch GmbH) in Stuttgart, with support on the outer piston. Radial piston pumps are known. In this radial piston pump, a molded batch cylinder has a plurality of cylinders, and radially slidable pistons are arranged in the cylinders. These pistons are supported by the inner circumferential surface of the stroke ring disposed in the leak chamber of the pump, which is almost impossible to rotate in a radially outward manner through the slide shoe with respect to the cylinder of the molding arrangement. These pistons are held in the stroke ring by the medium to be pushed.

Each slide shoe has a cutout in the middle of its sliding surface to achieve hydrostatic, ie hydrostatic, bearing load reduction of the sliding bearing formed by the stroke ring and slide shoe. This cutout part is connected to each cylinder chamber. In the operation of such a known pump, the slide shoe always moves in one direction along the inner circumferential surface of the stroke ring.

A swash plate axial piston pump is known in accordance with Bosch-Hydraulik Information und Daten, 1970/71, page 57. In this axial piston pump, the axial piston pump is disposed in the corresponding hole of the pump body, and the pump body is driven by the drive shaft. The piston is supported by the working surface of the swash plate installed in the leak chamber of the pump via the slide shoe. The slide shoe is kept in contact with the swash plate by the pressing ring.

In the hydrostatic bearing of the sliding bearing formed by the swash plate and the slide shoe, a cutout in the middle of the slide surface of the slide shoe is connected to each work room to achieve load reduction. Even in this known pump, the slide shoe always moves in one direction along the working surface of the swash plate during operation.

Another known radial piston pump (German Patent No. 3726957 specification) has a piston guided in a cylinder disposed in the casing. The piston is driven via an eccentric body by a drive shaft. A slide shoe is attached to the piston to support the piston on the outer surface of the eccentric body. The notch is provided in the support surface mounted on the outer surface of the eccentric body of this slide shoe. This cutout is connected to a correspondingly arranged work chamber for reducing hydrostatic bearing load. The effective area of the cutout required as the bearing load reducing portion is smaller than the effective area of the piston. Even in such known pumps the slide shoe always moves in the same direction relative to the support bearing surface of the eccentric.

The object of the present invention is to improve the piston pump of the type mentioned at the outset so that wear of the bearing surfaces reciprocally reciprocates, i.e., scaffolding, which occurs when the medium is poorly lubricated, for example, fuel, especially gasoline. ) To reduce concerns.

In order to solve this problem, in the structure of this invention, the load reduction chamber formed by the notch part provided in the area | region of a slide surface and a sliding bearing surface is connected to a work room.

An advantage of the piston pump according to the invention is that the hydrostatic load reduction of the sliding bearing between the piston and the stroke ring can be achieved by the connection of the load reducing chamber and the working chamber. This reduction in load significantly reduces the risk of scuffing even in bearings with sliding surfaces that reciprocate, so that the pump is particularly suitable for poorly lubricating media, e.g. fuels, when very high pressures on the discharge side are to be provided. In particular, it can be used to pump gasoline. The hydrostatic load reduction of the sliding bearings also significantly reduces friction. This can reduce the drive output of the pump.

This friction reduction reduces the tilting moment acting on the piston to be fixed by the guide surface of the piston in the casing and further reduces the wear of the piston guide portion. This increases the service life of the piston pump according to the present invention.

That is, according to this invention, the hydrostatic load reduction of the surface which slides in a piston pump is performed. In this piston pump, the rotational drive motion of the drive shaft is not directly converted to the linear motion of the piston, but first is changed to the non-rotating circulation motion of the stroke ring driving the piston. This generates distributed support or support of the piston in the drive shaft. This support has a sliding bearing formed by the sliding surface of the piston and the sliding bearing surface of the stroke ring. This sliding bearing catches the reciprocating linear motion and is hydrostatically relieved in accordance with the present invention. Moreover, the support part has a bearing of a stroke ring in a drive shaft or the crank element arrange | positioned at this drive shaft. The bearing of this stroke ring allows the rotation of the stroke ring relative to the drive shaft.

In particular, when the compressive force between the sliding surface corresponding to the piston and the sliding bearing surface of the stroke ring is independent of the feed pressure generated during the discharge stroke by appropriately setting the effective area of the load reduction type in comparison with the effective piston area, desirable.

The use of a spring restricts the compressive force to repelling force, in particular, to push the piston onto the stroke ring during its suction stroke, i.e. to always ensure a positive, positive positive pressure between the sliding surface and the sliding bearing surface. It can be made smaller than repulsion force.

In addition, in the gap between the sliding surface arranged correspondingly to the piston and the sliding bearing surface of the stroke ring, and in the gap between these support surfaces when the piston is supported by the slide shoe via the support surface stand, in particular during the discharge stroke The sliding film is formed based on the pressure gradient between the working room, the load reducing room and the low pressure room. This sliding film further reduces friction. Such a reduction in friction can further reduce the tilting of the piston relative to the piston guide, especially in the discharge stroke. The reason for this is that the stroke ring which reciprocates at right angles to the piston axis during pump operation rarely transmits the lateral force to the piston.

Advantageous configurations of the piston pump according to the present invention are obtained by the means described in claim 2 below.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a planar partial sectional view of a piston disposed in a shape of a piston pump according to the present invention.

2A is a cross-sectional view of the pump element of the piston pump of FIG.

Fig. 2B is a cross-sectional view of the mounting area of the slide shoe from the piston pump of Fig. 1 to the stroke ring.

3 is a cross-sectional view of a pump element of another piston pump according to the present invention;

4 is a cross-sectional view of a pump element of another piston pump according to the present invention;

Explanation of symbols on the main parts of the drawings

10 casing 11: pump element

12, 12 ': piston 13: piston guide

14: holder 15, 15 ': slide shoe

15 clamp 16 sliding surface

17: sliding bearing surface 18: stroke ring

19: crank element 20: sliding bearing

21: spring 22, 22 ': load reducing room

23: through opening 24: passage

25: working room 26: valve body

27: pressure valve 28: high pressure chamber

29 closed portion 30 through hole

31: inflow area 32: valve spring

33: low pressure chamber 34: suction opening

35: edge 40: suction hole

41: valve body 42: intake valve

43: suction groove 44: valve spring

50; Step 51: Supporting surface

52: cut out 54: shoulder

55: receiving ring

Next, examples of the present invention shown in the drawings will be described.

As shown in FIG. 1, the piston pump according to the present invention has a casing 10. In this casing, for example, three pump elements 11 are arranged for molding. The number of pump elements 11 may increase or decrease depending on the desired uniformity of the pressure formed by the piston pump.

Each pump element 11 has a piston 12. This piston is slidably supported in the piston guide 13. This piston guide 13 is held in the casing 10 by the holding part 14. In the embodiment shown in the figure, the piston guide 13 is shown as a separate component, but a guide for the piston 12 may be formed directly in the casing 10.

Each piston 12 supports the slide shoe 15 which has the slide surface 16 in the edge part which protruded from the piston guide 13. As shown in FIG. Through this slide shoe, the piston 12 is supported by a hub ring 18, that is, a cam ring, which generates the stroke of the piston on the sliding bearing surface 17. This stroke ring is rotatably supported by a crank element 19, for example an eccentric pin or a drive shaft. It is preferable that a bearing means, for example, a sliding bearing 20, is provided between the stroke ring 18 and the crank element 19.

One piston 21 is disposed on each piston 12 so that the piston 12 and the slide surface 16 corresponding to the piston are always in contact with the stroke ring 18 during the operation of the piston pump. . This spring is supported by the support 14 at one end, and is supported by the slide shoe 15 via the crank 15 holding the slide shoe 15 on the piston 12 at the other end. The slide shoe 15 further pushes the piston 12 against the stroke ring 18 in the direction away from the holding portion 14.

Since the crank element 19 is arranged with an eccentric distance e with respect to the drive shaft axis A, each piston 12 is driven and reciprocates in the piston guide 13. The stroke of this reciprocating motion is twice the eccentric distance e, that is, 2e. The stroke ring 18 is reciprocated by a distance 2e with respect to the corresponding piston 12 in parallel with respect to the corresponding sliding bearing surface 17 and at right angles with respect to the drive shaft axis A, respectively.

In particular, during the discharge stroke of the piston 12, that is, when the piston 12 is pushed upward into the piston guide 13 as shown in FIG. 2 (a), the slide shoe 15 is stroked. In order to reduce the compressive force pushed against the ring 18, the load reducing chamber 22 opened to the sliding bearing surface 17 of the stroke ring 18 is provided in the slide shoe 15. The load reducing chamber 22 is connected to the work chamber 25 of the pump element 11 via the through opening 23 provided in the slide shoe 15 and the passage 24 in the axial direction.

As shown in FIG. 2B, a cutout is provided in place of the load reducing chamber 22 of the slide shoe 15, or in addition to the load reducing chamber 22, on the sliding bearing surface 17 of the stroke ring 18. Can be installed. As a result, the load reducing chamber 22 'is formed in the stroke ring 18. As shown in FIG.

The working chamber 25 in the piston guide 13 is divided by the piston 12 on one side and by the valve body 26 of the pressure valve 27 on the other side. This pressure valve separates the working chamber 25 from the high pressure chamber 28. This high pressure chamber is provided in the holding part 14 between the piston guide 13 and the closing part 29 inserted in the holding part 14.

The high pressure chamber 28 is connected to the inflow area 31 of the discharge conduit which is not shown through the radial through hole 30. This discharge conduit runs through a high pressure connection. The closure 29 is used as a receiving portion for the valve spring 32. This valve spring pushes the valve body 26 to the piston guide 13.

Advantageously of the embodiment of the invention shown in FIG. 2A in order to be able to supply a pressurized medium, in particular fuel or gasoline, to a work chamber 25 in a low pressure chamber 33 installed in a casing 10. In this case, a suction valve is provided on the wall of the piston 12. This suction valve has a radial suction opening 34 in the piston 12. This suction opening connects the passage 24 and the outside of the piston 12. This suction opening 34 is controlled by the edge part 35 of the piston guide 13 used as a control edge part.

In the operation of the piston pump according to the present invention, as shown in FIG. 2A, after the intake opening 34 is closed by the piston guide 13, during the discharge stroke, that is, the piston 12 is shown in FIG. 2A. The pressure of the medium confined in the work chamber 25, the passage 24 and the load relief chambers 22 and 22 'is increased while being moved upwards. This pressure increase is caused by the force applied to the valve body 26 of the pressure valve 27 by the pressurized pressurizing medium in the working chamber 25 by the force of the valve spring 32 and the pressurizing medium in the high pressure chamber 28. The pressure is applied to the valve body 26 until it is larger than the closing force acting on the valve body 26.

During the discharge stroke, the slide shoe 15 is applied by the medium in the load reducing chambers 22 and 22 'against the pressure pushed on the stroke ring 18 by the pressure formed in the spring 21 and the working chamber 25. Pressure on the slide shoe 15 generates a force that is turned in the opposite direction in the stroke ring 18. When the effective area of the load reducing chambers 22 and 22 'is larger than the effective area of the piston 12, the force applied to the slide shoe 15 by the piston 12 is completely compensated and generated by the spring 21. Power is partially compensated. When setting the effective area of the load reducing chambers 22 and 22 ', the slide surface 16 and the stroke ring of the slide shoe 15 are sufficiently sealed to sufficiently seal the load reducing chamber 22 so that a desired high feed pressure is obtained. Since a positive surface pressure must always exist between the sliding bearing surface 17 of 18), it should be taken into account that the force generated by the spring 21 is not completely compensated.

The piston 12, the slide shoe 15, and the stroke ring 18 are located inside the low pressure chamber 33. During the entire stroke of the piston 12, the slide surface 16 of the slide shoe 15 is fitted to the sliding bearing surface 17 of the stroke ring 18. During rotational movement of the crank element 19, the stroke ring 18 slides along the slide surface 16 of the slide shoe 15 based on the eccentric distance e (FIG. 1). When viewed from the direction of such relative movement, the length of the sliding bearing surface 17 of the stroke ring 18 is sufficiently dimensioned so that the load reducing chamber 22 does not exceed the end of the sliding bearing surface 17 (FIG. 2A). The length of the slide surface 16 of the slide shoe 15 is sufficiently dimensioned so that the load reducing chamber 22 'does not exceed the end of the slide surface 16 (FIG. 2B). This ensures that the medium pressurized in the work chamber 25 is not undesirably returned to the low pressure chamber 33 from the load reducing chambers 22: 22 'during the discharge stroke.

That is, the load reducing chamber 22 and / or 22 ', the sliding surface 16 and the sliding bearing surface 17 have the load reducing chamber 22 and / or 22' at any position of the stroke ring 18. Even in the low pressure chamber 33, the dimension is set so that it may be closed. During the discharge stroke, the load reducing chambers 22 and 22 'are surrounded by the contact portion between the slide surface 16 and the sliding bearing surface 17 at any position of the stroke ring 15.

After opening the pressure valve 27 at the end of the discharge stroke, the pressure in the work chamber 25, the passage 24, and the load relief chamber 22 falls below the pressure causing the closing of the pressure valve 27, and thus the piston 12. As soon as the suction stroke, i.e., the downward movement as shown in Fig. 2A, is started, negative pressure is generated in the work chamber 25, the passage 24, and the load reducing chamber 22 immediately. This is because the suction opening 34 is still closed by the piston guide 13 at this point. By this, the outstanding force against the spring 21 does not work and the piston 12 is moved to move out of the piston guide 13. As soon as the suction opening 34 reaches the edge 35 of the piston 13 and is released, fuel is released from the low pressure chamber 33 through the suction opening 34 and the passage 24 to reduce the load in the working chamber 25. The pressure compensation between the low pressure chamber 33, the working chamber 25, and the load reduction chamber 22 is generally performed in the chamber 22. As shown in FIG.

In the working chamber 25, in the passage 24, in the load relief chamber 22, and in the low pressure chamber 33, unless the suction opening 34 is open during the remaining suction stroke and not yet fully closed during the subsequent discharge stroke. In general, approximately the same pressure is formed.

The effective area of the load reducing chamber 22 is selected to be smaller than the effective area of the piston 12 and is only partially compensated for the pressing force between the slide shoe 15 and the stroke ring 18 formed during the discharge stroke by the piston 12. It is thought that it is not obtained. However, as the pressure in the working chamber 25 increases, the surface pressure between the sliding surface 16 and the sliding bearing surface 17 also increases, so that the load reducing chamber 22 for the low pressure chamber 33; 22 ') sealability is improved. It is preferable that the effective area of the load reducing chambers 22; 22 'be at least the same size as the effective area of the piston 12, or selected larger than the effective area of the piston. In the former case, the pressing force for the slide shoe 15 is already adjusted mainly by the spring 21. In the latter case, on the other hand, as the pressure in the work chamber 25 and the load reducing chambers 22 and 22 'increases, part of the repulsive force that is increased during the discharge stroke is compensated. However, the effective area of the load reducing chambers 22 and 22 'is that the force applied to the direction in which the slide shoe 15 is spaced apart from the stroke ring 18 is determined by the repulsive force of the spring 21 and the pressure in the working chamber 25. It should not be larger than the sum of the forces exerted on the piston 12.

In the case of the piston pump according to the present invention, the medium to be pumped is for example pumped into the low pressure chamber 33 at a voltage of about 3 bar, whereas the starting pressure of the piston pump is 60-120 bar or more. Therefore, the surface pressure between the slide shoe 15 and the stroke ring 18, that is, between the slide surface 16 and the sliding bearing surface 17 is significantly reduced. This is particularly advantageous if the lubrication of the fuel, in particular gasoline, is poor.

The slide shoe is pushed against the stroke ring 18 so that the sliding bearing surface 17 of the stroke ring 18 slides along the sliding surface 16 of the slide shoe 15 with respect to the longitudinal axis of the piston 12. Friction force acting on the piston 12 is generated via the slide shoe 15 in the horizontal direction. As the surface pressure is reduced by the pressure in the load reducing chambers 22 and 22 ', the friction between the slide shoe 5 and the stroke ring 18 is reduced even in the case of a medium having poor lubricity. The force exerted on the piston 12 by friction by the stroke ring 18 in the transverse direction relative to the axis (this force results in a tilting moment acting on the piston 12) is significantly reduced. This increases the service life of the pump according to the present invention. This is because the wear of the face of the piston guide 13, which must support the tilting force or tilting moment that guides the piston 12, is reduced.

Figure 3 shows another embodiment of a piston pump according to the present invention. This piston pump differs from the embodiment shown in FIG. 2A in that the suction path between the low pressure chamber 33 and the work chamber 25 is arranged.

The stroke ring 18 has a radial suction hole 40 in the area of each sliding bearing surface 17. This suction hole is enlarged on the funnel toward the sliding bearing surface 17. Thereby, for example, a receiving portion for the spherical valve body 41 of the intake valve 42 is formed. The suction hole 40 is opened in the suction groove 43 connected to the low pressure chamber 33 at the radially inner side, that is, at the end portion which faces the sliding bearing 20. The suction groove is provided in the inner bearing surface which extends substantially in the axial direction and cooperates with the sliding bearing 20 of the stroke ring 18. The valve spring 44 disposed in the load reducing chamber 22 is supported between the slide shoe 15 and the valve body 41 of the intake valve 42. As a result, the valve body 41 is pressed to the seat portion.

As shown, instead of supporting the valve spring 44 to the slide shoe 15, a spring holder or support yoke is installed on the stroke ring 18 that does not obstruct the flow path through the intake valve 42 and the valve spring ( It is also conceivable that 44 is mainly held by the stroke ring 18 and further deformed by the sliding motion between the slide shoe 15 and the stroke ring 18.

In the operation of the piston pump according to the present invention described with reference to FIG. 3, the intake valve 42 is formed and closed by the valve spring 44 at the start of the discharge stroke after the intake stroke of the piston 12 ends. While the piston 12 is sliding toward the work chamber 25 during the discharge stroke, the pressure in the work chamber 25 and the load relief chamber 22 is raised until the pressure valve 27 is opened. As a result, when the effective area of the load reducing chamber 22 is larger than the effective area of the piston 12, the increase in the repulsive force generated by the spring 21 is compensated or the excessive compensation is performed by overcompensation. The compressive force acting on 15) can be kept constant or reduced. As a result, the friction between the slide shoe 15 and the stroke ring 18 can be kept constant or reduced during the discharge stroke.

Immediately after the suction stroke starts, the suction valve 42 opens and the medium to be pumped slides in the low pressure chamber 33 with the suction groove 43, the suction hole 40, the suction valve 42, the load alleviation chamber 22 and the slide. It is sucked into the working chamber 25 through the through opening 23 of the shoe 15 and the passage 24 of the piston 12. As a result, pressure compensation is already performed at the start of the suction stroke, so that the pressure in the work chamber 25 and the load reduction chamber 23 is only slightly smaller than the pressure in the low pressure chamber 33. That is, the pressing force is formed by the spring 21.

In another embodiment of the piston pump according to the invention, as shown in FIG. 4, the suction opening 34 of the piston 12 also has a stroke ring 18 between the suction groove 43 and the load reducing chamber 22. ), A suction valve 42 is also provided.

In addition, the piston 12 'has a spherical or spherical end section 50. The spherical support surface 51 of this section is supported by the corresponding support surface 53 of the mutually inclined notch 52 provided in the slide shoe 15 '. The end segment 50 of the piston 12 'is provided with the shoulder 54 on the opposite side to the slide shoe 15'. A receiving ring 55 for the shoulder 21 is mounted.

Such support of the piston 12 'to the slide shoe 15' is also possible in the embodiment shown in FIGS. 2A, 2B and 3. Similarly, the fixed form of the slide shoe 15 in the piston 12 shown in these figures can also be used in the embodiment of the present invention shown in FIG.

In the case of the piston pump according to the present invention shown in FIG. 4, the hydrostatic load reduction of the slide shoe 15 ′ is performed during the discharge stroke as in the embodiment shown in FIG. 2A. The illustrated piston pump works almost the same as that shown in FIG. After releasing the suction opening 34 in the piston 12 ', the same conditions as in the embodiment shown in FIG. 2A are brought about.

After the suction opening 34 is opened, suction of the medium to be conveyed is performed by the suction opening 34 and also by the suction hole 40 of the stroke ring 18. The fruit paste cross section can be formed smaller than the embodiment shown in FIG. 2A or FIG. 3.

The piston 12 'is supported by the spherical or spherical end segment 50 to compensate for the tilting motion of the piston 12' in the piston guide 13 which may be generated based on manufacturing error. Can be. The gap between the support surface 51 of the piston 12 'and the support surface 53 of the slide shoe 15' is reduced in load by a film made of a medium to be fed during the discharge stroke. This is because the pressure in the passage 24 and in the load alleviation chamber 22 is relatively high and the medium to be conveyed is pushed into the low pressure chamber 33 through such a gap.

An advantage of the piston pump according to the invention is that the hydrostatic load reduction of the sliding bearing between the piston and the stroke ring can be achieved by the connection of the load reducing chamber and the working chamber. This reduction in load significantly reduces the risk of scuffing even in bearings with sliding surfaces that reciprocate, so that the pump is particularly suitable for poorly lubricating media, e.g. fuels, when very high pressures on the discharge side are to be provided. In particular, it can be used to pump gasoline. The hydrostatic load reduction of the sliding bearings also significantly reduces friction. This can reduce the drive output of the pump.

Claims (11)

One or more pistons are provided, the pistons being movably supported in the casing, dividing the workroom in the casings, drive shafts supported in the casings, crank elements mounted on the drive shafts, The stroke ring is supported to allow relative rotational movement, and the stroke ring is not rotatable in the casing, and the stroke ring has a sliding bearing surface corresponding to the piston, and the piston has a sliding surface on the bearing surface. In the piston pump of the type supported and the piston is loaded by the drive shaft, A piston pump characterized in that the load reducing chamber (22) formed by the cutouts provided in the areas of the slide surface (16) and the sliding bearing surface (17) is connected to the working chamber (25). 2. The load reducing chamber (22) according to claim 1, wherein the load reducing chamber (22) is formed by the cutout of the sliding surface (16) disposed on the piston (12), and is opened toward the sliding bearing surface (17) of the stroke ring (18). Piston pump characterized in that. The piston pump according to claim 1 or 2, wherein the load reducing chamber (22) has an effective area equal to or larger than the effective area of the piston (12). The piston pump according to claim 1, wherein the piston (12) is pressed against the stroke ring (18) by a spring (21). The low pressure chamber (10) according to claim 1, wherein the crank element (19) is provided in the casing (10) with a distinction protruding from the stroke ring (18) and the piston guide (13) of the piston (12) supported by the stroke ring. 33) and The low pressure chamber is used as a supply chamber for the medium to be conveyed, The piston 12 has a passage 24 opened in the working chamber 25, The passage (24) is connected to the low pressure chamber (33) via a suction valve (34, 35; 42). 6. The suction valve (34) according to claim 5, wherein the suction valve is formed by a suction opening (34) provided in the wall of the piston (12), and the suction opening cooperates with an edge portion (35) of the piston guide (13) used as a control surface portion. Piston pump, characterized in that. 6. The load reducing chamber (22) is connected to the low pressure chamber (33) via the suction hole (40) and the suction groove (43), and the suction valve (42) is disposed in the suction hole (40). Piston pump characterized in that. 8. The low pressure chamber (33) according to any one of claims 5 to 7, wherein the passage (24) of the piston (12) and the load reducing chamber (22) pass through the suction valves (34, 35, 42), respectively. Piston pump, characterized in that connected to. The inclined cutout portions of the slide shoe 15 'on the spherical or nominal support surface 51 of the short segment 50, wherein the piston 12 protrudes from the piston guide 13. 52) The slide shoe supports the slide surface 16 corresponding to the piston 12 on the opposite side to the cutout 52, A gap formed between the support surface 51 of the piston 12 and the support surface 53 of the slide shoe 15 ′ is connected to the connection portions 24 and 23 of the work chamber 25 and the load reducing chamber 22. Piston pump characterized in that. 10. Piston pump according to claim 9, characterized in that the spring (21) is supported on the piston (12). 5. The slide surface (16) according to claim 4, wherein the spring (21) is supported by a slide shoe (15) attached to the piston (12), the slide shoe correspondingly arranged on the piston (12) opposite the piston (12). Piston pump characterized in that for supporting).